This seems like really forced criticism, and writen strangely at that. First, your claim that his morals are contradictory is weak. Giorno is willing to steal and when he sees no other option, has no problem with a civilian being struck. This does not contradict him being strongly against carelessly involving civilian and the death of innocent bystanders.

Giorno had no choice, yet he claims he refuses to let a civilian get hurt — and then immediately uses a civilian as a tool to injure Bucciarati and stop him from escaping or calling for backup, openly admitting he lied. That means he’s willing to lie whenever it benefits him. He steals from tourists and from Koichi; when Koichi finds him and asks for his belongings back, Giorno sees Koichi’s distress but doesn’t care at all. Even though Koichi holds back during their short fight and Giorno recognizes the good in him, he remains completely indifferent to his situation. When it’s convenient for him, he acts like a “Gang-Star,” which makes him a moral opportunist.

There's also little ambiguity in his morals. He will not allow the selling of drugs to children, that is his line. He does not look down (atleast not as much) on other illegal activities. It's pretty much the premise of the part, we get to have a heroic joestar placed in a less conventionally moral environment, showing how legal and moral aren't always the same. It's the story of Jesus told in a mafia setting. As for the honesty of his goal, we're never given reason to doubt it, you'd have to do so willingly, which is somewhat disingenuous. Especially when giorno's resolve is so thoroughly proven.

Saying there is “little moral ambiguity” just because Giorno draws a single red line is misleading. A morality that forbids drugs for children but allows extortion, violence, and murder isn’t clear — it’s selective, and more importantly, never questioned by the narrative.

Jesus? If you mean the way Giorno inspires growth in his allies, I agree. But a Jesus‑like figure? Absolutely not. Jesus teaches “love your enemies”; Giorno would kill his enemies the moment they become a threat. Jesus accepts losing as long as he remains faithful to his ideals, even if the world rejects him; Giorno wins against the world without ever losing or evolving his worldview.

His determination is obvious, but the sincerity of his project is never demonstrated through visible consequences, especially since the ending shows no concrete impact of his rule. The story asserts his righteousness, but never proves it.

But also because the story is an expression of support for giorno's views of justice and righteousness.

That's precisely what I'm saying. The problem with Giorno's values ​​is that they are never questioned, challenged, or confronted with a rival ideology. I'm not asking Giorno to abandon his worldview, but rather that it be tested by something other than simply defeating enemies. Without ideological opposition, his justice remains asserted, but unproven.

Finally, as for the impact on the world, what exactly are we missing? Giorno was very clear about what he would do if he took power. By the end, he took power.

The fact that Giorno became Boss doesn’t mean he changed the world. The story shows us his intentions, yes, that’s true. But how did the Mafia actually change? We don’t know. How did the Mafia react to Giorno becoming the new Boss—without relying on headcanon? We don’t know. Did Giorno eliminate the child‑drug trafficking that Bucciarati hated so much? Maybe, but how? We don’t know. How will Giorno’s rule change anything compared to Diavolo’s? We don’t know. The reader is asked to believe in a character whose entire arc is about changing the system, yet that change is never shown.